The Chemistry of the Human Sebaceous Gland*

View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector THE CHEMISTRY OF THE HUMAN SEBACEOUS GLAND* I. HISTOCHEMICAL OBSERVATIONS RAYMOND R. SUSKIND, M.D. WITH THE TECHNICAL ASSISTANCE OF CLARA KEENAN, ANN PRESNELL AND JEAN SEBASTIANI The chemical processes which occur in the formation of normal sebum have been the concern of investigators for many years. The problems of determining the constituents of sebaceous secretion have been approached by various investigators from several directions. The first approach attempted was to study surface lipids. Attempts to analyze surface sebum were made as early as 1886 by Krukenberg (1), who collected lipids from the skin surface with blotting paper. More recently Engman and Kooyman (2), Emanuel (3, 4), Rothman et al. (5, 6, 7), Weitkamp et al. (8), Butcher and Parnell (9), Kirk (10), Kvorning (11) and Kile, Snyder and Haefele (12) have collected surface lipids by various methods and determined several constituents quantitatively. A second method of approach has been that of studying the secretion or lipid material within the individual pilosebaceous structure and within the cells of the sebaceous acini. The investigators (13, 14-48) who have studied the individual gland have employed histochemical technics to localize and identify the different classes of lipid substances. Both of the above methods of approach have apparent limitations. Surface lipids cannot be said to be derived exclusively from the sebaceous glands. It has been known for a long time that normal epidermal cornification contributes cholesterol and perhaps other lipids to surface "sebum". There is still uncon- tradicted evidence that the sudoriparous glands may contribute fatty substances to the lipid covering of the cutaneous surface. The sum total of these fatty substances is probably acted upon by fat-splitting enzymes on the cutaneous surface and may account for the free fatty acids and higher alcohols which have been reported in surface lipid analyses. Hence, surface lipids are essentially chemically contaminated sebum. A third possible approach to the problems of the biochemistry of the human sebaceous gland is to conduct quantitative analyses of sebum collected from individual glands. The technical difficulties in the methods of collection and micro- analysis are undoubtedly great, but not insurmountable. Histochemical methods for lipids have their own inherent limitations. Many of the present methods lack absolute specificity. Several methods for lipids, *Fromthe Kettering Laboratory in the Department of Preventive Medicine and In- dustrial Henith, and the Department of Dermatology and Syphilology, College of Medicine, University of Cincinnati. This work was made possible by n grant from the Bristol-Myers Company, New York, N.Y. Read before the Society for Investigative Dermatology, San Francisco June 26, 1950. 37 38 THE JOURNAL OF INVESTIGATIVE DERMATOLOGY which still find their way into present day investigations, have been proved to have little or no histochemical validity (19). The conjoint application of several methods, each of which meets conditions which establish its histochemical validity (20), provides a series of scientific clues. When the set of clues is inte- grated, fundamental information may be obtained about the chemical processes in a cell, a gland or a skin appendage such as the pilosebaceous apparatus. Human sebaceous glands have been studied carefully with histochemical methods in one recent work by Montagna, who limited his observations to the glands of the human external auditory meatus (17). He and his co-workers previously demonstrated that considerable information may be obtained about the cytochemical constituents of the sebaceous glands of small mammals (l4-- 16, 18). With these facts in mind, a series of experiments were undertaken to attempt to find out what chemical information concerning lipids and related enzymes of the human sebaceous gland might be obtained by means of histochemical methods. It was the purpose of these experiments to attempt to identify and localize different classes of lipids in the human sebaceous glands in apparently normal skin, and to compare this information with similar histochemical observations of altered pilosebaceous structures such as are seen in acne vulgaris, occupational acne and cutaneous cysts of possible sebaceous origin. MATERIALS Sixty-one specimens of normal skin were obtained by biopsy or from post-mortem examinations from 24 persons ranging in age from new born to 92 years. This group of persons included 13 white males, 7 white females and 4 colored males. The areas of skin which were obtainable from post-mortem examinations included specimens from presternal, shoulder, interscapular, and scalp regions. In one instance specimens of skin of the ala nasi were obtained. Four post mortem specimens from the pubic area were included in the series. Nine specimens of skin involved with early lesions of acne vulgaris were obtained from 4 patients: 2 white females and 2 white males, whose ages ranged from 13—22. They included comedones, papules and nodules. Four comedones were examined for cholesterol. Two comedones were examined for alkaline phosphatase activity. Eleven biopsy specimens of early lesions of occupation acne (chloracne) were obtained from four patients who developed severe generalized acne as a result of exposure to tn- chlorphenol or its polymer. The skin eruption was accompanied by systemic manifestations, persistent increased prothrombin time, hypercholesteremia and hyperlipemia. These patients had clinical evidence of hepatic disease, recurrent peripheral neuritis and mild central nervous system symptoms. Six cutaneous cysts, diagnosed clinically as wens, were excised in toto from scalp, tem- poral area, back and chest of five adult persons. Histologically the cysts fulfilled the criteria for the diagnosis of epithelial cyst (31, 32). Two of the six cysts had, in addition, charac- teristics of sebaceous cysts (32). METHODS All normal and abnormal specimens on which lipid detection methods were employed were fixed in Baker's formal-calcium and embedded in gelatin (21). In order to prevent loss of content of epithelial cysts, these six specimens were fixed in formal-calcium for 10 to 12 months. Prior to embedding, a portion of each specimen was treated with potassium dichromate (22) as a method of mordanting and rendering insoluble phospholipids for CHEMISTRY OF HUMAN SEBACEOUS GLAND 39 staining with acid hematin. All of the specimens except the larger cysts were frozen and cut lOp in thickness. Cysts were cut iSp in thickness. Sections of each specimen were stained with Sudan IV and Sudan Black to demonstrate localization of all classes of lipids. Sections were also stained with Nile blue sulfate (20). The detection of phospholipids was attempted with Baker's acid hematin technic (21, 22, 25). The technics employed to detect steroids were the Itomieu modification of the Lieber- mann-Burehard test (22), and treatment of sections with digitonin (22, 26). Unstained and untreated sections were examined under polarized light for birefringence. Alkaline phosphatase activity was studied in fresh biopsy specimens fixed in chilled acetone by the method of Gomori (27, 28). For purposes of histological identification and comparison, sections of all specimens were stained with hematoxylin and phloxine. OBSERYATIONS OF NORMAL TISSUES Sudan Colorants With few exceptions a rather distinct pattern of sudanophilic globule formation was noted in sebaceous gland acini in sections of skin from all age groups and all areas studied. At the fuadus of each acinus, the peripheral layer of sebaceous cells consisted generally of small cuboidal cells with relatively little cytoplasm, and an easily discernible centrally placed round nucleus. In the peripheral layer, or layers of fundic cells, sudanophilic globules were either absent, or were seen as small colored granules, few in number, and distributed throughout the cell (Fig. 4a, b, 7a). The more centrally located cells contained progressively greater numbers of sudanophilic globules which were larger in size. Subjacent to the acinar duct, their size was increased many fold and their cytoplasm filled with large sudanophilic globules (Fig. 4a, b). In the preductal portion of most active glands, large fat globules were admixed with shriveled nuclear particles. Lipid material commonly filled the entire duct and extended into the hair follicle. The sudanophilic substance extended from the duct, surrounded the hair shaft, covered the stratum corneum on the surface of the epithelium and was mixed with its keratin lamellae. In some of these sections, glands which had little or no sudanophilic material in the ducts and hair follicles, were frequently observed despite the usual pattern of lipid globule formation in the acini themselves. In two presternal specimens from persons in the older age group, the usual pattern of globule formation was not noted. The gland acini were small by comparison with the presternal sebaceous glands in the other subjects. The peripheral cells contained uniformly large globules, as did the central cells. This was noted in a 92 year old white man and a 70 year old white woman. When duplicate sections were treated with both Sudan IV and Sudan Black B, a difference in the staining capacity of the two colorants was noted. Sudan Black B not only stained the lipid globules much more intensely, hut stained

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